🔍 Key Concepts

• pump-down solenoid valve function in a recovery unit (what happens when it closes?) • how a restricted orifice affects flow rate and pressure in a liquid line • difference between changing recovery modes (liquid vs vapor) and preparing for shutdown/pump‑down of the machine

💭 Think About

• When the pump-down solenoid closes, where is refrigerant still allowed to move, and through what path? Think about what role the restricted orifice plays in that movement. • Ask yourself: is the system trying to move refrigerant from one mode path to another, or is it trying to clear refrigerant out of the unit before stopping or changing work? • Consider what an HVAC/R technician means by a pump‑down: what is being pumped down, from where, and for what reason?

✅ Before You Answer

• Verify whether pump‑down is normally associated with changing between liquid/vapor modes or with clearing refrigerant before shutdown/servicing. • Check if the restricted orifice allows a slow, controlled equalization or migration of refrigerant so the compressor can evacuate lines without slugging liquid. • Confirm in the illustration which side of the solenoid valve and orifice connects to the compressor suction and which connects to the refrigerant source/lines, and think about what that orientation implies about their purpose.